This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application PANEL OF CATHODE RAY TUBE filed with the Korean Industrial Property Office on the Feb. 29, 2000 and there duly assigned Ser. No. 10057/2000.
1. Field of the Invention
The present invention relates to a cathode ray tube (CRT), and more particularly, to a panel of a CRT having improved curvature and thickness of a screen surface where an image is formed.
2. Description of the Related Art
A typical color CRT includes a panel having a screen surface where a fluorescent film which emits light in three colors is formed, and a funnel coupled to the panel forming a housing of the CRT. Recent exemplars in the art include the Cathode Ray Tube With Specifically Shaped Inside Picture Area of H. Wakasono, U.S. Pat. No. 6,157,124, the Color Cathode Ray Tube of N. Shimizu, et al., U.S. Pat. No. 6,066,914, the Color Picture Tube Device Having Contoured Panel And Auxiliary Coil For Reducing Apparent Screen Distortions of K. Nakamura, et al., U.S. Pat. No. 6,133,681, and the Color Picture Tube of K. Nakamura, U.S. Pat. No. 6,046,540. A shadow mask frame assembly that is perforated by a plurality of holes which accommodate passage of electronic beams, is installed on the inner surface of the panel to be separated by a predetermined distance from the fluorescent film. An electron gun and a deflection yoke are installed at a neck portion and a cone portion of the funnel, respectively.
In the CRT having the above structure, a screen surface of the panel is formed such that the thickness of a central portion thereof is thinner than the thickness of a peripheral portion, in consideration of the high vacuum in the CRT and atmospheric pressure. The difference in thickness between the central portion and the peripheral portion of the screen surface causes a difference in brightness between the central portion and the peripheral portion of an image formed as the fluorescent film coated on the inner surface of the screen surface is excited. To overcome this difference in brightness, the current density of an electron beam impingent upon a fluorescent substance at the central portion of the screen surface is customarily reduced to lower the brightness of the central portion. In this case, the brightness of the overall image formed by the CRT is lowered. When it is desired to improve the brightness of the image, because both the sense of flatness of the outer surface of the panel and the convergence correction of the deflection yoke corresponding to the curvature of the inner surface of the panel must be taken into consideration, the design of the panel is, in my opinion, unnecessarily complex.
It is therefore, an object of the present invention to provide an improved cathode ray tube and process for manufacturing cathode ray tubes.
It is another object to provide a thinner panel for a cathode ray tube and a process for manufacturing a thinner panel for a cathode ray tube.
It is still another object to provide an improved panel and process for manufacturing panels for cathode ray tubes.
It is yet another object to provide a process for manufacturing and a panel that exhibits greater uniformity in cross-sectional thickness.
It is still yet another object to provide a process for manufacturing and a panel produced by that process that exhibits a greater degree of uniformity of brightness across the entirety of visual image formed on its screen surface.
It is a further object to provide a panel of a CRT in which the panel is lighter but is not susceptible to either implosion or to deviation of brightness attributable to differences in thickness of the panel.
These and other objects may be attained with an improved cathode ray tube and process for manufacturing a cathode ray tube. The panel is manufactured to provide that the thickness of the central portion of an effective area of the screen surface is TC, the thickness of a vertical edge of the screen surface is TV, the thickness of a horizontal edge of the screen surface is TH, and the thickness of an edge in a diagonal direction along the screen surface is TD. These respective values of thickness satisfy the expression of inequality:
(THxe2x88x92TC)+(TVxe2x88x92TC)+(TDxe2x88x92TC) less than TC/3,
and the radius of curvature of the outer surface when measured along the diagonal direction of the effective area is 1,450 millimeters or more.